Truing apparatus for lapping machines



June 1 1937. H. s. INDGE TRUING' APPARATUS FOR LAPPING MACHINES 3Sheets- Sheet 1 Filed Sept. 28, 1955 HERBERT 5'. INDG'E W ITNESS JMW Wm.wm

June 1, 1937.

H. S. INDGE TRUING APPARATUS FOR LAPPING MACHINES Filed Sept. 28, 1935 3Sheets-Sheet 3 Qrwam'tcw HERBERT 5.1m) GE W TNESS Patented June 1, 1937Herbert S. Indge, Westboro, Mass, assignor to Norton Company, Worcester,Mass, a corporation of Massachusetts Appiication September 28, 1935,Serial No. 42,583

7 Claims.

This invention relates to lapping or grinding machines, and moreparticularly to a lap or grinding wheel truing mechanism.

One of the objects of this invention is to provide a simple, thoroughlypracticable truing apparatus for truing the flat operative face of a lapor abrasive wheel. Another object is to provide a truing apparatus fortruing the opposed operative flat faces of two opposed lapping orgrinding wheels. Another object is to provide a truing apparatus whichis capable of truing the two opposed operative faces of a pair ofopposed lapping or grinding elements simultaneously.

A further object is to provide a pivotally mounted truing tool carrierfor swinging the truing tool or tools through an arcuate path across theoperative face or faces of a lap or grinding wheel. Another object ofthis invention is to provide a pivotally mounted truing tool holderwhich is rocked through an arcuate path across the face of the grindingwheel by a hydraulically actuated mechanism.

A further object is to provide a hydraulically 5 actuated mechanism forcontrolling the movement of a truing tool across the face of a lap orgrinding wheel, in which the truing speed may be readily controlled. Afurther object is to provide a hydraulically actuated mechanism formoving a truing tool through an arcuate path across the operative faceof a lap, in which both the intake and exhaust of fluid are throttled todefinitely control the rate of movement of the truing tool. Otherobjects will be in part obvi- 35 ous or in part pointed out hereinafter.

The invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts, as will beexemplified in the structure to be hereinafter described, and the scopeof the application of which will be indicated in the following claims.

In the accompanying drawings in which is shown one of various possibleembodiments of the mechanical features of this invention,

5 Fig. l is a side elevation of a lapping machine and truing apparatusembodying this invention, having parts broken away to more clearly showthe construction;

Fig. 2 is a fragmentary cross-sectional view,

50 on an enlarged scale, taken approximately on the line 2-2 of Fig. 1;

Fig. 3 is a combination cross-sectional view and elevation of the mountfor the truing apparatus taken approximately on the line 33 of Fig. 2;

Fig. ,4 is a fragmentary elevation, on an enlarged scale, of the pivotalsupport for the truing apparatus;

Fig. 5 is a cross-sectional View, on an enlarged scale, takenapproximately on the line 5-5 of Fig. 1;

Fig. 6 is a fragmentary cross-sectional view, on an enlarged scale,taken approximately on the line i6 of Fig. l, of the binder mechanismfor locking the upper lapping element in any desired position;

Fig. 7 is a cross-sectional View through the control valve, on anenlarged scale, taken approximately on the line l-'! of Fig. 2;

Fig. 8 is a cross-sectional view, on an enlarged scale, takenapproximately on the line 8-8 of Fig. 2;

Fig. 9 is a vertical section showing a modified form of mounting for thetruing tools;

Fig. 10 is a cross-sectional view, taken approximately on the linelfl-H) of Fig. 9, showing the clamping mechanism for the truing tools;and

Fig. 11 is a fragmentary cross-sectional view taken approximately on theline H-l I of Fig. 9, showing the adjusting mechanism for the truingtools.

In the embodiment of the invention selected for illustration, a lappingmachine has been shown comprising a base II adapted to support a lowerlap l2 and an upper lap I3. The upper and lower laps are arranged for arelative rotary motion to produce a predetermined lapping operation. Inthe preferred construction, both the upper and the lower laps arerotated preferably in different directions.

Power may be supplied to the machine in any convenient manner, such asby means of a belt arranged to rotate a pulley l5 keyed to a shaft 16journaled in bearings ll, l8, l9, and 20 in the base I lof the machineand arranged to rotate both the upper and the lower lap. A worm 2! isfastened to the shaft l6 and meshes with a worm gear 22 keyed to avertical sleeve 23 which is rotatably supported in a bearing 24 withinthe base of the machine. The upper end of the sleeve 23 supports aspider 25 which in turn supports the lower lapping wheel E2. The rotarymotion applied to pulley i5 is transmitted through shaft l6, worm 2i,worm gear 22, sleeve 23 and spider 25 to rotate the lower lap 52. Thedetails of the mounting for the upper lap have not been shown in detailin the present case, since they are not considered to be a part of thepresent invention. For further details, reference may be had to my priorPatent No. 1,870,328 dated August 9, 1932.

The lapping elements or wheels I2 and I3, as illustrated, are eachformed as an annulus of ceramic bonded abrasive grains made like agrinding wheel, each of which is provided with a substantially fiatabrading or lapping surface for simultaneously engaging and abrading orlapping the opposed faces of a Work piece.

The rotatable upper lap I3 is supported by means of a spider 30 mountedon the lower end of a rotatable spindle 3L The spindle Si is rotatablysupported in bearings (not shown) in a vertically movable sleeve 32which is slidably mounted within a projecting portion 34 of an arm 35.The arm 35 is formed integrally with a Vertically extending column 36which is fixed to the base II. The lap I3 and spindle 3! may be rotatedfrom any suitable source of power, but as illustrated in the drawings isdriven by means of a belt from the shaft I6. A pulley ll] is mounted onthe shaft I6 and is connected by means of a belt 4! with a pulley 42mounted on the upper end of the upper lap spindle M. The belt lI passesover a pair of idler pulleys 43 (only one of which has been illustratedin Fig. l) which are rotatably supported on a transverse shaft M. Itwill be readily apparent from the foregoing disclosure that rotation ofthe shaft It by means of driving pulley I5 serve to simultaneouslyrotate both the upper lap I3 and the lower lap i2.

In order that the laps I2 and I3 may be maintained with proper operativesurfaces for producing the desired lapping operation, a suitable truingapparatus is essential to permit a truing of the operative faces of thelaps when necessary. In the embodiment of the invention illustrated, apivotally mounted truing apparatus is provided in which a truing tool ismounted on a rock arm and arranged to be swung through an arcuate pathacross the operative face or faces of the lap. As illustrated in thedrawings, this mechanism comprises a vertically mounted rotatable shaft50 supported in bearings 5| and 52 on a bracket 53 which is rigidlymounted on the columns 36. An arm 54 is mounted on the shaft 50. The arm54 is provided with an elongated head 55 which is slotted at 55 andarranged to be clamped in adjusted position on the shaft 53 by means ofclamping screws 5'! and 58. The screws 51 and 53 pass through clearanceholes in bosses 59 and 66 and are screw threaded into bosses GI and 62so, that the head 55 may be readily clamped in adjusted position on thever-v tical shaft 5il. A push screw 65 is screw threaded in a boss 66and abuts against a boss 5?. This push screw serves to spread or expandthe head 55 when it is desired to unclamp the arm 54. An end thrust andlocating collar I0 serves to locate the head 55 in the desired positionon the shaft 50. The collar It is preferably a split collar and arrangedto be clamped in adjusted position on the shaft 59 by means of aclamping screw II. The shaft 5c is rotatably mounted in bearing brackets5i and 52 which are fixedly mounted on the column 36. A thrust washer orcollar '55 which fits on a reduced portion IS on the lower end of theshaft 50 and bears against the upper surface of bearing 52 serves totake up the vertical thrust of the shaft 50 and its associated parts. Asimilar collar or thrust washer 71 also fits on the reduced portion 76and is held in adjusted position by a pair of lock nuts I8 and IS. Thethrust collars l5 and TI together with the lock nuts 18 and I9 serve asan end thrust bearing to hold the shaft 56 in the desired verticalposition.

The outer end of the arm 54 is provided with an enlarged head 80 whichis arranged to support a pair of opposed diamonds or truing tools 8! and82, each of which is separately adjusted relative to the head Sfi. Thetruing tool 8| is mounted in the end of a spindle 83 which is slidablykeyed by means of key 83, in an aperture 85 within head 30. An adjustingscrew 86 is screw threaded into a threaded aperture 8'! in the spindie83 and serves to adjust the position of the spindle 8E and the truingtool 8I relative to the head 89. In order that the screw 86 may be heldagainst endwise movement, it is provided with an enlarged head 89 whichfits within a counterbored recess 98 in the head 80 and is held inadjusted position relative thereto by means of a cap or cover plate 9|.The diamond or truing tool 82 is held in a similar spindle 35 which isslidably keyed by means of a key 96 within an aperture 97 within thehead 88 and is arranged to be adjusted relative thereto by means of ascrew 98 which is screw threaded into a threaded aperture 99 within thespindle 95. The screw 98 is provided with an enlarged head II!!! whichfits within a counterbored aperture I Ell in the head 3i] and is held inadjusted position therein by means of a cover plate I02. It is readilyapparent from the foregoing disclosure that the diamonds or truing toolsBI and 82 may each be adjusted relative to the head by manipulation ofscrews 86 and 98.

In order that the diamonds or truing tools may be locked in adjustedpositions on the head 88, the opposite sides of the head are providedwith slots I55 and Iflfi which enable portions of the head to be sprungto bind the spindles 83 and in their adjusted position. A binding screwI Ill passes through a clearance hole in a boss I88 and is screwthreaded into a boss I09 t0 clamp the spindle 83 and diamond BI in thedesired adjusted position. A binding screw IIIl passes through aclearance hole in boss III and is screw threaded into boss II2 to serveas a clamp for the spindle 95 and the diamond 82 in the desired adjustedposition. It will be readily apparent from the foregoing disclosure thatthe diamonds BI and 82 may be readily and precisely adjusted relative tothe head lit by manipulation of the clamping screws Iil'l and H6 and.the adjusting screws 36 and 98.

To attain one of the objects of this invention, it is desirable toprovide a suitable power operated mechanism for moving the truing toolsacross the face of the laps l2 and I3 at a slow uniform rate to true theoperative faces thereof to form the desired lapping surfaces. In thepreferred construction, a hydraulically actuated mechanism is providedto swing the arm 54 to pass the truing tools 8! and 82 through anarouate path across the operative fiat faces of the lapping wheels. Afluid pressure cylinder I26 is pivotally mounted on a stud IZI which isin turn supported in a bracket i522 projecting from the column 36. Apiston I23 is slidably mounted within the cylinder 529 and is connectedby means of a piston rod I2 3 with a stud I25. Stud I25 is alsoconnected with one end of a connecting rod I26, the other end of whichis pivotally connected to a stud I27. The stud I2? is connected to oneend of a rock arm I29, the other end I30 of which is locked to the upperend of the shaft Ell by means of a set screw I3I. It will be readilyapparent from the foregoing disclosure that when fluid is admitted tothe cylinder I20, causing the piston I23 to move therein, this motionwill be transmitted through the connecting rod I24, stud I25, connectingrod I26, to rock the arm I29 which in turn serves to rock the verticalshaft 50 and thereby swing the arm 54 and the truing tools 8| and 82across the operative faces of the laps I2 and I3.

A fluid pressure system is provided to sup-ply fluid under pressure tooperate the piston I23. This system comprises a reservoir II5 within thebase of the machine. A pump II6 draws fluid from the reservoir II5through a pipe I32 and forces fluid under pressure through a pipe I33 toa control valve I34. A pressure relief valve I35 is connected in thepipe line I33 to return excess fluid through an exhaust pipe I36 to thereservoir I I5. The control valve I34 is of a slidable piston type andcomprises valve pistons I38, I39, and I40 which are formed integrallywith a valve stem I4I. This valve serves as a reversing valve and also aspeed control or throttle valve to control the direction and speed ofmovement of the truing tool or tools across the operative faces of thelaps. Fluid under pressure from the pipe I 33 enters a valve chamber I42formed between the valve pistons I38 and I39 and passes out through apipe I43 into a cylinder chamber I44 to cause the piston I23 to movetoward the right, as viewed in Fig. 2, which serves to rock the arm 54in a counterclockwise direction. During this movement of the'arm 54,fluid under pressure exhausts from a cylinder chamber I45, a pipe I46, avalve chamber I48 formed between valve pistons I39 and I40 and outthrough an exhaust pipe I49 and through the pipe I36 into the reservoirH5.

The valve stem MI is provided with an operating knob or handle I50. Whenit is desired to reverse the direction of movement of the arm 54 so asto cause the truing tools to move in a clockwise direction (Fig. 2), theknob I50 is moved into a position I50a, as shown in broken lines in Fig.2, which serves to shift the valve pistons I36, I39, and I40 into areverse position so that fluid under pressure from the pipe I33 willpass through valve chamber I48 between the valve pistons I39 and I40 andthrough pipe I46 into a cylinder chamber I45 to cause the piston I23 tomove toward the left, as viewed in Fig. 2, so as to swing the arm 54 andthe truing tools BI and 82 in a clockwise direction through an arcuatepath across the operative faces of the laps I2 and I3. During thismovement of the piston I23, fluid under pressure exhausts from thecylinder chamber I44 through the pipe I43, the valve chamber I42 betweenthe pistons I38 and I39, and out through a pipe I52 and the pipe I36 tothe reservoir II5.

In order that the laps I2 and I3 may be trued to produce the desiredlapping surface, it is desirable to provide a speed controlling devicefor the fluid pressure system so that a slow uniform traverse of thetruing tool across the face of the laps may be obtained. This ispreferably accomplished by providing a suitable arrangement forthrottling the. fluid passing through the control valve I34. In thepreferred construction, the valve I34 is provided not only with alongitudinal motion to cause a reversal of the direction of flow offluid within the system but is also provided with a rotary motion whichserves to throttle the flow of fluid through the valve. The valve is soconstructed that both the intake and exhaust of fluid are throttled tothe same extent to provide a slow uniform movement of the truing tool.

The valve stem MI is provided with a serrated portion I55 which isengaged by a spring pressed plunger I56 so that the valve stem I4I maybe readily rotated to the desired position and held in the adjustedposition. the fluid passing to and from the control valve, the valvepistons I 38 and I 40 are each provided with throttling grooves I60(Figs. 2 and 8). There are four openings or holes I59 through the valvesleeve I6I and four grooves I60 which extend longitudinally of the valvepiston I40 forming lands I55 therebetween. By rotating the valve stemI4I, the lands I between the grooves I68 may close the valve sleeveopenings I59 to a greater or lesser extent to throttle the flow of fluidtherethrough. Fig. 8 shows a cross section through the valve taken onthe line 8-8 of Fig. 2 through the valve piston I40. The valve pistonI38 is similarly provided with grooves and lands so that the fluidentering or exhausting from the valve chamber I42 may also be throttledto the same extent. It will be readily apparent from the foregoingdisclosure that by endwise movement of the valve stem I4I, the fluidunder pressure within the system may be reversed to move the piston I23in either direction so as to move the truing tools either in a clockwiseor counterclockwise direction across the face of the laps to be trued.By rotating the knob I50 and valve stem I4I, the fluid entering orexhausting from the system may be varied from the maximum to a pointwhere the fluid is entirely out off, that is when the lands I65 (Fig. 8)are turned to entirely block the ports I59 in the valve sleeve I6I. Byrotating the valve stem to the desired extent, the speed of movement ofthe truing tools may be accurately controlled to produce the desiredlapping surface.

It may be desirable to arrange the truing tools BI and 82 in axialalignment and diametrically opposed to each other so that both of thelaps I2 and I8 may be simultaneously trued. A modified construction hasbeen illustrated in Figs. 9, l0, and 11, in which the truing tools 8|and 82 are arranged diametrically opposite to each other. The arm 54, asshown in Figs. 9, l0, and 11, is provided with an enlarged head ISIhaving a vertically extending aperture I92 arranged to receive a pair ofdiamonds or truing tool holders I93 and I94. The truing tool holder I94is provided with a reduced threaded portion I95 which engages or mesheswith a threaded aperture I96 within the diamond holder I93. A pair ofbinding screws I91 and I98 are arranged to bind the diamond holders I93and I94 in place on the head. Details of only one of the clampingmechanisms have been illustrated since they are both identical inconstruction. As shown in Fig. 10,

In order to throttle the clamping screw I9! passes through a clearancehole in a slidably mounted bushing 200 and is screw threaded into acentral aperture within the slidably mounted bushing 20I. The bushings200 and 20I are each provided with a transversely extending fragmentarycylindrical surface 202 and 203 respectively which are shaped to matewith the periphery of the truing tool holder I93 and I94 respectively.It will be readily apparent from the above disclosure that when thescrew I9! is tightened, the bushings 200 and 20I are drawn together toclamp the diamond holder I93 in adjusted position.

In order that the truing tools 8| and 82 may be readily and separatelyadjusted, the inner ends of the truing tool holders I93 and I94 areformed as .a spiral gear 255 and 206 respectively. A pair of spiralgears 251 and 208 mesh with the gears 205 and 205 respectively. Gears2G1 and 208 are mounted on rotatable shafts 209 and -2I0 respectivelyand are arranged to be adjusted by knobs ZII and 2I2 respectively. Thebinding screws I91 and I98 are maintained in a clamped position exceptduring adjustment of the diamonds 8| and 82. If it is desired to adjustthe diamond 82, the clamping screw I98 is loosened to unclamp the holderI94 while the clamping screw I81 is in a clamped relationship to holdthe diamond holder I93 against rotation. Then the knob M2 is turned torotate the shaft ZIO, spiral gear 208, spiral gear 295, which serves torotate the diamond holder I94. This movement rotates the screw I55within the threaded aperture I96 and due to the fact that the holder I93is stationary serves to cause an endwise movement of the holder I94 toadjust the diamond 82 as desired.

Similarly, when it is desired to adjust the position of diamond BI, theclamping screw I98 is locked in a clamping position to prevent rotationof the holder I94. The clamping screw I91 is unclamped to permitrotation of the holder I93 and the adjusting knob 2II is rotated tocause a rotation of the spiral gear 201 which serves to rotate spiralgear 265 and thereby cause a rotation of the diamond holder I93. Due tothe fact that the threaded projection I95 is held stationary, thethreaded aperture I96 is rotated on a fixed threaded portion I95 andcauses an endwise motion of the holder I93 to adjust the diamond BI asdesired.

The upper lap I3 is arranged to be moved vertically with relation to thelower lap. This may be accomplished either by means of a manuallycontrolled or automatically controlled mechanism. For the sake ofsimplicity of illustration, a manually operable mechanism has beenprovided comprising a hand wh eel I10 which is mounted on the outer endof a shaft I1I, the inner end of which carries a gear IBI meshing with arack bar I 32 on the vertically movable sleeve 32. By manipulating thehand wheel I15, the upper lap may be raised or lowered as desired. Thismechanism serves to bring the upper lap into operative relation with thework during the lapping operation and also serves to lower the lap untilthe operative face of the lapengages the truing tool for a truingoperation.

In order that the upper lap may be held against vertical movement in afixed position during the truing operation, means are provided to lockthe sleeve 32 in an adjusted truing position. This mechanism comprises aclamping screw I85 which comprises two slidably mounted bushings I86 andI81 each of which is provided with a partial cylindrical surface I88 andI89 respectively, which engage the periphery of the sleeve 32.. Theclamping screw I 85 passes through a clearance hole in the bushing I86and is screw threaded into an. aperture I53 in the bushing I81. Bytightening the screw I85, the bushings I86 and I81 are drawn together toclamp the sleeve 32 in rigid engagement with the projection 34 of'thearm 35 so as to lock the upper lap in a truing position. Truing tool BImay then be oscillated through an arcuate path across the operative faceof the lap I3 by oscillating the arm 54 by means of a fluid pressuremechanism.

In the operation of this truing apparatus, the

arm 54 is adjusted vertically on the shaft 50 and clamped in adjustedposition by means of the locating collar 10 and the arm is then clampedin position thereon by means of the clamping screws 51 and 58. The lapI2 is then set in rotation and the valve I34 operated by means of theknob I50 serves to pass the truing tool 82 across the operative face ofthe lower lap. By adjusting the screw 98, the truing tool 82 may bebrought into the desired truing relation with the operative face of thelap I2. The truing tool may then be oscillated through an arcuate pathacross the face of the lap until the lap is trued to the desired extent.By adjusting the position of the truing tool, any amount of material maybe trued from the lap as desired.

To true the upper lap I3, the hand wheel I10 is rotated to turn the gearI8I which meshes with the rack bar I82 on vertically movable sleeve 32.By manipulating the hand wheel I10, the upper lap I3 may be lowereduntil the operative face of the lap engages the truing tool 8|. Thesleeve 32 may then be locked in a truing position by means of theclamping screw I85. The truing tool 8I may then be oscillated through anarcuate path across the operative face of the lap I3 by oscillating thearm 54 by means of the fluid pressure mechanism. By turning theadjusting screw 86, the diamond or truing tool 8| may be preciselyadjusted relative to the lap I3 to true its operative surface to thedesired extent.

In the operation of the modified construction, the truing toolsupporting arm 54 is moved so that the diamond 82 is oppositeto the lapI2.

The diamond 82 is then adjusted downwardly to contact with the surfaceof the lap I2. The upper lap I 3 is then lowered by manipulation of thehand wheel I10 so that the operative surface of the lap I3 is broughtinto truing engagement with the truing tool 8|. Then, by manipulation ofthe fluid pressure mechanism, the truing tools may be passed through anarcuate path relative to the laps I2 and I3 to simultaneously true theopposed operative surface of the two laps.

It will thus be seen that there has been provided by this inventionapparatus in which the various objects hereinabove set forth togetherwith many thoroughly practical advantages are successfully achieved.

As many possible embodiments may be made of the above invention and asmany changes might be made in the embodiment above set forth, it is tobe understood that all matter hereinbefore set forth, or shown in theaccompanying drawings, is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. An abrasive wheel truing apparatus comprising a rotatable abrasivewheel, a movable truing tool support, a truing tool adjustably mountedthereon, means to feed the truing tool relatively toward and from theoperative face of said abrasive wheel, means including a fluid pressurepiston and cylinder to move said support to pass the truing tool acrossthe operative face of said wheel, and a control valve for regulatingboth the direction and speed of movement of the truing tool relative tothe operative face of said abrasive wheel.

2. A truing apparatus for a lapping machine comprising a rotatablelapping wheel having an operative fiat face, a movable truing toolsupport, a truing tool adjustably mounted thereon,

means to adjust the truing tool to feed the tool toward and from theoperative face of said lapping wheel, means including a fluid pressurepiston and cylinder to move said support and traverse the truing toolacross the operative face of said lap, and a single control valvetherefor, said valve being movable in one direction to control thedirection of movement of the truing tool and movable in a seconddirection to control the speed of movement of the truing tool relativeto said lap.

3. A truing apparatus for a lapping machine comprising a rotatablelapping wheel, a pivotally mounted truing tool support, a truing tooladjustably mounted thereon, means to adjust the truing tool relative tothe support to permit feeding the truing tool toward and from theoperative face of said lapping wheel, means including a fluid pressurepiston and cylinder to swing the support so as to traverse the truingtool across the operative face of said lap, a fluid control valvetherefor, and a manually operable means to move said valve in onedirection to change the direction of movement of the truing toolrelative to the lap and to move said valve in a second direction to holdit in a predetermined position to regulate the speed of movement of thetruing tool relative to the operative face of the lap.

4. A truing apparatus for a lapping machine comprising a rotatablelapping wheel having an operative flat face, a movable truing toolsupport, a vertical pivot for said support, a truing tool adjustablymounted thereon, means to adjust the truing tool to feed the truing tooltoward and from the operative face of the lapping wheel, means includinga fluid pressure piston and cylinder to swing said truing tool acrossthe face of said lap, a single control valve therefor, and means to movesaid valve longitudinally in one direction to reverse the movement ofthe truing tool and to rotate and hold said valve in a predeterminedposition to control the speed. of movement of the truing tool across theoperative face of said lap.

5. A truing apparatus for a lapping machine comprising a rotatablelapping wheel, a pivotally mounted truing tool support, a truing tooladjustably mounted thereon, means to adjust the truing tool to feed thetool toward or from the operative face of the lap, means including afluid pressure piston and cylinder to move said support to traverse saidtool across the face of said lap, a control valve therefor, and means tomove said valve longitudinally to reverse the direction of movement ofthe truing tool relative to the lap and to rotate and hold said valve ina desired rotary position to throttle both the intake and exhaust offluid to and from said cylinder to control the speed of movement of thetruing tool relative to the operative face of said lap.

6. A truing apparatus for a lapping machine comprising a pair of opposedflat relatively rotatable lapping wheels, a movably mounted truing toolsupport, a pair of opposed truing tools adjustably supported thereon,means to independently adjust each of said tools relative to thesupport, means including a fluid pressure piston and cylinder which areoperatively connected to move said support to simultaneously traversethe truing tools across the operative faces of said lapping wheels, anda control valve for regulating both the direction and speed of movementof the truing tools relative to the operative faces of said lappingwheels.

7. A truing apparatus for a lapping machine comprising a pair of opposedflat relatively rotatable lapping wheels, a movably mounted truing toolsupport, a pair of opposed truing tools adjustably supported thereon,means to independently adjust each of said tools relative to thesupport, means including a fluid pressure piston and cylinder which areoperatively connected to move said support to simultaneously traversethe truing tools across the operative faces of said wheels, and acontrol valve in said system which serves when moved in one direction toreverse the direction of movement of the truing tool and when rotatedserves to throttle the fluid under pressure to control the speed ofmovement of the truing tools across said lap.

HERBERT S. INDGE.

